Is Spot Happy? Just Look At His Tail

If you're a dog lover, how many times have you asked yourself, "what is he or she thinking about anyway?"

We fuss over our dogs, worry about them, spend more than $38 billion to keep them happy and healthy. But how do we know really what they are feeling?

It turns out that the tail tells the story, CBS News correspondent Richard Schlesinger reports.

A wagging tail doesn't always equal a happy dog. Italian researchers videotaped how 30 dogs wagged their tails after seeing different things.

They measured the angle of the wag and concluded if it the tail favors the dog's left side, he's not so pleased about what he sees. On the right side, he's happy.

"When the dog is wagging its tail, the dog is saying a lot," says Dr. Stephen Zawistowski. He's an expert in animal behavior and is excited by the new study. Schlesinger met him at The Wagging Tail, an aptly named doggie day care facility in New York.

"The nature of that wag, by parsing it very carefully, we're seeing that it's signaling some elements of intention or how the dog is interpreting the situation," Zawistowski says.

Schlesinger says he never thought his dog, Sally, had any trouble at all telling him how she feels.

"She's usually pretty happy. But that's just my opinion — it's not very scientific," he says.

The scientists slowed down the video tape for accurate measurement.

"They're taking a protractor looking at the deflection of the tail. Most of us are not going to be able to be that careful in reading something like that," Zawistowski says.

Most of us will rely on more old-fashioned ways of judging the happiness of our dogs — tried and true, although not particularly scientific.